The Muscular System

1. The Muscular System Chest Wall Abdominal Wall Trunk

2. Chest Wall

3. External Intercostals • External Intercostals • ORIGINInferior border of ribs as far back as posterior angles • INSERTIONSuperior border of ribs below, passing obliquely downwards and backwards • ACTIONFix intercostal spaces during respiration. Aids forced inspiration by elevating ribs

4. Internal Intercostals • Internal Intercostals • ORIGINInferior border of ribs as far back as posterior angles • INSERTIONSuperior border of ribs below , passing obliquely downwards and backwards • ACTIONFix intercostal spaces during espiration. Aids forced inspiration by elevating ribs

5. Diaphragm • Diaphragm • ORIGINVertebral:crura from bodies of L1, 2 (left), L1-3 (right). Costal: medial and lateral arcuate ligs, inner aspect of lower six ribs . Sternal: two slips from posterior aspect of xiphoid • INSERTIONCentral tendon • ACTIONInspiration and assists in raising intra-abdominal pressure

6. Abdominal Wall

7. External Oblique • External Oblique • ORIGINAnterior angles of lower eight ribs • INSERTIONOuter anterior half of iliac crest, inguinal lig, public tubercle and crest, and aponeurosis of anterior rectus sheath • ACTIONSupports abdominal wall, assists forced expiration, aids raising intraabdominal pressure and, with muscles of opposite side, abducts and rotates trunk

8. Internal Oblique • Internal Oblique • ORIGINLumbar fascia, anterior two thirds of iliac crest and lateral two thirds of inguinal ligament • INSERTIONCostal margin, aponeurosis of rectus sheath (anterior and posterior ), conjoint tendon to pubic crest and pectineal line • ACTIONSupports abdominal wall, assists forced respiration, aids raising intra-abdominal pressure and, with muscles of other side , abducts and rotates trunk. Conjoint tendon supports posterior wall of inguinal canal

9. Transverses Abdominis • Transverses Abdominis • ORIGINCostal margin, lumbar fascia, anterior two thirds of iliac crest and lateral half of inguinal ligament • INSERTIONAponeurosis of posterior and anterior rectus sheath and conjoint tendon to pubic crest and pectineal line • ACTIONSupports abdominal wall, aids forced expiration and raising intra-abdominal pressure. Conjoint tendon supports posterior wall of inguinal canal

10. Rectus Abdominis • Rectus Abdominis • ORIGINPubic crest and pubic symphysis • INSERTION5, 6, 7 costal cartilages, medial inferiorcostal margin and posterior aspect of xiphoid • ACTIONFlexes trunk, aids forced expiration and raise intra-abdominal pressure

11. QUADRATUS LUMBORUM • Quadratus Lumborum • ORIGINInferior border of 12th rib • INSERTIONApices of transverse processes of L1-4, iliolumbar ligament and posterior third of iliac crest • ACTIONFixes 12th rib during respiration and lateral flexes trunk

12. Trunk

13. Iliopsoas • Iliopsoas • ORIGINIliac crest, sacrum, lumbar vertebrae • INSERTIONRibs, cervical transverse processes • ACTIONExtends and lateral flexes spine

14. Erector Spinae • Erector Spinae • ORIGINSpinous processes • INSERTIONSpinous processes six levels above • ACTIONLateral flexion of spine